Power line communication (PLC) systems are well known in the art. See, for example, the book entitled “The Essential Guide to Home Networking Technologies” published in 2001 by Prentice-Hall, Inc., copending U.S. application Ser. No. 09/290,255, filed Apr. 12, 1999, the web site http:/www.homeplug.org of the Home Plug Special Interest Group and the article entitled “Home Plug Standard Brings Networking to the Home” in the December 2000 issue, Vol. 16, No. 12, of the Communication Systems Design magazine.
Power line communications for access is a powerful technology that offers the consumer many real advantages over other forms (e.g., DSL, cable modems, etc.). These advantages include: power distribution networks to all homes and businesses are already in place, and PLC technology has been demonstrated to work at high data rates, as well as many other advantages. One of the problems solved by this invention is making the communications connection in a low cost manner between the power line distribution cables or wires, such as the pole-mounted cables or wires (any segment of the power line distribution network applies here including, but not limited to the LV (low voltage) and MV (medium voltage) networks and the home or business offices. Connecting to the power distribution network can be difficult and expensive requiring turning off network power during installation.
Power line communication systems of the type to which the invention relates apply modulated radio frequency carriers, e.g. carriers having frequencies in the range from about 2-9 MHz for access and from about 5 MHz to 20 MHz, for in home communications to power lines.
Electrical power distribution systems, commonly used in the United States, distribute the electrical power at 60 Hz from the source over cables, insulated or uninsulated. At the source, the voltage is high, e.g., over 200,000 volts and by means of transformers, the voltage is reduced by a transformer or transformers to a medium voltage, e.g., of the order of 20,000 volts, to be delivered to consumers by at least three cables or wires suspended from poles. At some of the poles, there are transformers which further reduce the voltage to low voltage of the order of 117 volts between a cable and a ground or neutral cable for the delivery of power to one or more customers or consumers. The power lines from the output of a pole transformer to the customers premises connect to a power consumption meter which in turn connects to the wiring in the customer's premises (e.g., home power wiring).
While the pole transformer and the power consumption meter cause comparatively little power loss at the low frequency at which the power is supplied, both the transformer and the meter can cause substantial radio frequency, communication signal power loss. Therefore, a parallel communication signal electrical path around at least the pole transformer has been provided to improve the communication signal power in the premises wiring. However, the prior art proposals for the parallel path have involved conductive (galvanic) connections both at the input and output of the pole transformer which requires skilled installers and in at least some cases, interruption of the power during installation of parallel path, by-pass equipment.
An object of the invention is to improve the transfer of communication signal power at the input of a lossy element, such as a low frequency transformer or a power consumption meter, to a power line or other equipment at the output side of the lossy element and particularly, to increase the communication signal power in the consumer's premises' wiring, and thereby improve the operation and reliability of the communication system without requiring interruption of the delivery of electrical power and without conductive connections to the medium voltage power lines.